1. Field of the Invention
This invention relates to a numerical control (NC) data creation method and, more particularly, to an NC data creation method through which a machining process sequence is decided so that a workpiece machined in accordance with the machining process sequence can be machined into a desired shape and that such machining can be performed very efficiently.
2. Description of the Related Art
In a machining center, a blank is machined into a desired shape via a plurality of machining processes. For example, predetermined face milling, pocket machining, contour machining and drilling processes are applied to each and every face of a blank to machine the blank into a desired shape.
Conventionally, automatically creating the NC data for such machining processes entails the following:
(a) defining the machining processes, machined shape, tools, machining conditions and the like for every machined face;
(b) editing of each machining process (i.e. defining the sequence of the machining processes); and
(c) creating NC data, using the data inputted at step (a), in accordance with the machining process sequence decided in the machining process editing operation.
The machining process editing operation of step (b) is necessary for the following reason: In the machining definition step (a), great value is placed upon the ease with which definitions can be made. Therefore, if NC data were created for the purpose of performing machining merely in the order of the definitions, there would be causes in which the desired shape could not be obtained with the NC data or, even if the desired shape could be obtained, the machining would be performed inefficiently, resulting in a prolonged machining time. Accordingly, in the machining process editing operation of step (b), the machining process sequence is altered so as to minimize the number of tool changes without disturbing the sequence of those machining processes that must be performed in a certain order (i.e. those processes having machining sequence dependence).
FIG. 11 is a view for describing "machining sequence dependence". In FIG. 11, pocket machining (P1 or P2) is performance after face milling (F), and this is followed by drilling processes (D1, D2). More specifically, pocket machining (P1) must be performed after face milling (F), and drilling (D1) must be carried out after pocket machining (P1). Further, pocket machining (P2) must be performed after face milling (F), and drilling (D2) must be carried out after pocket machining (P2). However, once face milling has been performed, it does not matter whether pocket machining P1 or P2 is performed first. A case where a machining process must be completed before another machining process is carried out represents a machining process limitation and such processes are referred to as having "machining sequence dependence".
Accordingly, in the machining processing editing of step (b), machining processes that are dependent upon a machining sequence are specified and it is necessary to decide a machining process sequence that will reduce the number of tool changes so that machining will be performed efficiently.
Conventionally, however, difficulties are involved in specifying, through a simple manipulation, machining processes having machining sequence dependence, and in deciding machining processes through which machining can be performed efficiently while the machining sequence dependence is maintained.